1. Field of the Invention
The present invention is related generally to the field of separating solid and liquid components from a mixture. More specifically, the present invention is related to an improved filter plate assembly and related methods and filtering devices.
2. Description of the Related Art
Separating the liquid and solid components of a liquid-solid mixture, or slurry, is a necessary or desirable process in many industries. In many filtering applications, the slurry is a waste product and it is desirable to separate the solid and liquid matter and dispose of them separately. Often, the solid component may be a hazardous material and the liquid component may be reused or recycled. In other applications, the liquid component may be the final product, such as in the juice industry, for example. In this application, the solid component is desirably separated from the liquid to provide purity and clarity to the juice.
One method for separating liquids and solids is known as surface filtering. In a surface filtering process, the liquid-solid mixture is passed through a filter element under the influence of gravity or a relatively low pressure. The liquid component of the mixture passes through the filter element while the solid component is retained primarily on the surface of the filter element. However, with this type of filtering process, once the surface of the filter element is substantially covered with solid particulate matter, liquid is no longer able to pass through the filter element. The filter element must then be cleaned or replaced. Thus, surface filter processes are useful only for filtering slurries having a low concentration of solid matter.
Another method of filtering slurries having relatively high concentrations of solid matter uses an apparatus known as a filter press, which operates under a displacement filtering principle. A filter press utilizes a series of filter plates placed adjacent to one another. A space is defined between each pair of the filter plates and each space is lined with filter media. Typically, each of the filter plates includes a central aperture to permit all of the spaces between each pair of plates communicate with one another. An inlet is provided to introduce slurry into the interconnected spaces on an upstream side of the filter media. One or more outlets communicate with each space on a downstream side of the filter element.
Slurry is introduced through the inlet to fill all of the individual spaces between the filter plates. Once the spaces are filled, the delivery pressure of the incoming slurry is increased such that the liquid component is displaced through the filter media and the solid particulate matter is retained within the spaces upstream from the filter media. The filtered liquid, or filtrate, moves to the outlet(s), where it is discharged. The filter cycle continues until each of the spaces is substantially filled with particulate matter. Thus, the filter press utilizes substantially the entire volume of the spaces rather than relying on the surface area of the filter media, as is the case with surface filtering methods.
The solid particulate “cake” remaining in each individual space after the filter cycle must be removed in preparation for a subsequent filter cycle. The removal of the particulate cake may be accomplished manually or, in some instances, automatically. In either case, the filter plates must be separated from one another at least a distance equal to the thickness of the particulate cake to permit the particulate cake to be discharged from the filter cavity. Because as many as a hundred or more individual plates may be used, the cleaning process is very time-consuming and results in excessive down-time in which the filter press is not utilized. In addition, the filter press must be substantially longer than a length of the filter plates in order to provide space to separate the plates. Furthermore, due to the provision of multiple plates which need to be separated, fully automated filter cleaning systems employed with conventional filter presses are complex and often prohibitively expensive.